Nowadays, from environmental considerations, resins derived from plants, which are independent of petroleum based raw materials and consequently bring small environmental loading, are attracting attention. Among such resins derived from plants, polylactic acid resins for which the raw materials are plants such as corn and sweet potato are advantageous from the viewpoint of the resources, have biodegradability, and further are excellent in transparency, heat melt moldability and heat resistance, so as to reach the stage of practical use. For example, molded bodies such as films or sheets using polylactic acid resins are put to practical use.
However, in application of these molded bodies, these molded bodies have room for improvement with respect to the mechanical properties, the barrier property and the like thereof. Examples of a technique for solving these problems may include the production of composite materials involving different types of resin materials. For example, by laminating different types of films such as a polyolefin film excellent in the barrier property and the flexibility on polylactic acid resin films, conceivably shortcomings of polylactic acid resin films may be compensated.
For the purpose of compensating the shortcomings of a polylactic acid resin substrate by laminating the polylactic acid resin substrate and a polyolefin resin substrate on each other, it is essential that both of these substrates are not delaminated at a stage of practical use so as to allow the laminate to be practically usable. However, both of these substrates barely adhere to each other. Therefore, for the purpose of making both of these substrates adhere to each other, an attempt to use an adhesive has been made (JP2006-326952A). For example, for the adhesion between a polylactic acid resin substrate and a polyolefin resin substrate or the like, an investigation with respect to the use of a polypropylene-based resin composition for use in adhesion or the use of the like has also been performed (JP2005-263997A). However, no hitherto known adhesives have attained sufficient adhesiveness with respect to the adhesive strength between a polylactic acid resin substrate and a polyolefin resin substrate, and disadvantageously delamination or the like occurs during the use of products obtained through adhesion to consequently leave room for investigation of the adhesiveness improvement.
On the other hand, it has been known to use a composition of a graft modified ethylene/α-olefin random copolymer grafted with an unsaturated carboxylic acid or a derivative thereof, as a composition for use in adhesion, to a polymer that hardly adheres to a polyolefin typified by polyester such as polyethylene terephthalate, polycarbonate or the like (JP61-270155A, JP62-158043A). However, this composition for use in adhesion does not achieve a sufficient adhesion when applied to the adhesion between the polylactic acid resin substrate and the polyolefin resin substrate.